Traditional video editing systems are generally divided into two categories: linear and non-linear. Linear editing systems are generally integrated with tape-based program storage, while non-linear editing systems are associated more closely with disk-based storage media, wherein random-access storage more easily may be implemented. The typical linear editing system is implemented with one of the many "broadcast quality" videotape recording formats. The choices for analog recorders include, among others, 1" C-format, Betacam, Betacam-SP, 3/4" U-matic, U-matic-SP, S-VHS, and Hi-8. The choices for digital recorders include, among others, D-1, D-2, D-3, D-5, DCT, and Digital Betacam. Each of these recording formats is incompatible with any other format, and all require sophisticated system facilities, including synchronization systems, edit controllers, audio and video switchers and processors, digital video effects (DYE) systems, character generators, and other equipment. This, in turn, requires extensive physical plant facilities for electric power, air conditioning and air filtration, storage space, and maintenance equipment. Furthermore, large operational and maintenance staffs are required to keep the equipment in good working order. However, recording duration capacity for these types of videotape recorders ranges up to three hours or more, making them uniquely valuable for many applications, such as program distribution, archival storage, and as master program sources for mass duplication of videos for the home video market.
In contrast, non-linear systems are based on optical discs, or alternatively, on magnetic or magneto-optical disks. Because of the relatively high cost of these storage media when long-duration recording periods are required, such systems are relegated to use as off-line editing systems applied to the preparation of edit decision lists (EDLs) for use in edit suites incorporating linear editing systems. However, the rapid random-access features and editing ease are valuable for short programs.
As currently implemented by many manufacturers (such as AVID and videoCube), PC-based hard disk storage is very expensive. If equipped with 10 GB of storage capacity, the system, in practice, is utilized in a two-step process. First, the original unedited program material is digitized at a high data-compression ratio to provide representative pictures for use in an off-line editing environment, whereby the operator may develop an EDL. This EDL then is used to perform the required editing, using program materials that have been digitized and stored at much lower data-compression ratios. Because these two digitizing steps must be performed in real time, this is an expensive, time-consuming process which requires well-trained and expensive operational and engineering personnel.